This device relates generally to a circuit breaker for a computer cable. More particularly this device relates to a lock switch for enabling and disabling the line that carries data between an input device and a computer, such as a keyboard or mouse, thereby controlling access to the computer while leaving it running.
The use of computers has become increasingly popular. In addition to privately-used computers, computers are now being provided for commercial public use. This satisfies the need for those who do not have their own computers or who need particular software applications that are too costly to purchase for only occasional personal use. As more information and software is stored on computers, a need arises to protect this information from unauthorized access. For example, proprietors desiring to rent computers to users on a time-share basis must be able to limit or monitor the amount of time the computer is in use. A convenient method of controlling this is by limiting access to the computers.
Another situation requiring preventing unauthorized access is in the case of computers used to demonstrate software. Vendors have a need to prevent individuals from accessing, and potentially vandalizing or pirating, demonstration software until a trained attendant is available to assist them. In both these situations it is desirable to leave the computer running while concurrently preventing a user from using it. Leaving the computer on allows the software programs to continue to run, thereby permitting quick start-up when desired. Leaving the computer on also allows messages, instructions, or advertising to show on the monitor. This is particularly desirable for commercial settings.
A variety of devices have been used to prevent unauthorized access to computers. One method of access control is provided by a password system in the computer's software. This approach is disadvantageous, however, in that software passwords can be lost, bypassed, or divulged. Other devices known in the art for controlling access to a computer include mechanical devices that cover the computer's power switch, disk drive, or keyboard. This approach is disadvantageous in that mechanical covers are cumbersome and necessarily unique to the ever-changing physical configuration of the components. Both of these approaches are inconvenient and particularly unsuitable to the commercial use market.
Internal keyboard locks are known in the art and work by employing an electrical switch inside the computer that disables the function of the keyboard. Internal keyboard lock switches using a round, soda machine-style key are common for IBM-compatible personal computers. Such switches allow the key to be removed from the lock in either the enable or disable position. These devices are disadvantageous because users can unlock the keyboard and remove the key from the lock switch, leaving the computer vulnerable to unauthorized access. Furthermore, when these devices are turned to the off position, the computer may not continue to run. Re-start may be time-consuming and may cause unpredictable data loss.
U.S. Pat. No. 4,975,550 to Panchisin discloses an external keyboard lock that encases the keyboard port of a computer. This device has a housing that mounts to the surface of the computer surrounding the port. A key switch provided on the wall of the housing switches the power supply line to the keyboard, thereby selectively enabling or disabling the keyboard. The Panchisin device is disadvantageous because it must be permanently mounted over the keyboard port to avoid unauthorized users from circumventing access control. As the size of computers and the space between ports decreases, it may not be possible to mount the Panchisin device over the keyboard port without covering other ports on the computer. However, making the device detachable to use adjacent ports destroys the device's functionality.
More importantly, many modern computer operating systems fail to function if a keyboard is not properly attached to the keyboard port. If the power to the keyboard is shut off, the computer may be unable to acknowledge that the keyboard is still attached. By switching the power supply line to the keyboard, the Panchisin device not only disables the function of the keyboard, but the device also disables the function of the computer's operating system. This is disadvantageous because continued unattended operation of the computer, alone or as a server for other computers, may be desired while preventing unauthorized access to the computer via the keyboard.
Therefore, it is an object of this invention to provide a security device that will prevent unauthorized access to a computer. It is another object of this invention to provide a security device that disables the input device but allows continued operation of the computer. It is yet another object of the present invention to provide a security device that allows a key to be inserted and removed only when the input device is in the disabled state. It is yet a further object of the preset invention to provide a security device that switches only the line effectuating data flow of the input device cable and does not switch the power source. It is a another object of this invention to provide a security device that mounts to the cable of an input device.